Articulated joint between two shafts

ABSTRACT

Articulated joint comprising a cylindrical hollow drive element (2) and a spherical drive element (5) at the end of in each case one shaft (1,2), in which the hollow drive element (2) is roughly shaped like a hollow cylinder with a wavy inner profiling and the spherical drive element (5) has a spherical shape with a wavy profiling complimentary thereto, in such a way that even on pivoting the shafts with respect to one another there is a positive connection and reliable force transfer during rotation (FIG. 1).

FIELD OF APPLICATION

This invention relates to articulated joints, particularly of the typefor coupling shafts that pivot with respect to each another.

PRIOR ART

In known articulated or hinged joints, a first drive element at the endof a first rotary shaft pivotably engages a second drive element at theend of a second rotary shaft in a manner that allows the shafts to pivotwith repsect to each other through a given angle. Such articulatedjoints are known as cardan or universal joints.

In the past, such joints were excessively complex, required largeamounts of space, could not easily be encapsulated, or could not readilyaccommodate both high and low drive powers.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the invention is to improve joints of this type.

Another object of this invention is to eliminate the aforementioneddisadvantages.

According to the invention an articulated joint of the aforementionedtype is constructed in such a way that it is formed from simpleelements, has a limited space requirement, can be easily encapsulatedand can be readily used for large and small drive powers.

According to the invention this problem is solved in that the firstdrive element is roughly shaped like a hollow cylinder having on theinner surface axis-parallel, uniformly circumferentially distributed,alternately convex and concave depressions and elevations which passinto one another and that the second drive element is roughly sphericaland on its surface has alternating depressions and elevations, which inthe longitudinal direction run approximately in accordance with a planecontaining the axis of the second shaft and which in the circumferentialdirection and in particular in the equatorial plane of the sphericalsecond drive element have a configuration roughly complimentary to theinner surface of the first drive element.

In the case of such an articulated joint, the two shafts can be pivotedfrom a position in which the axes are aligned by a given amount in arandom direction.

In the construction according to the invention, the first drive elementis provided on its inside and the second, spherical drive element on itsoutside with in each case one wavy line profile which, considered in theaxle direction, comprises groove-like depressions and web-likeelevations. Much in the same way as the teeth and gaps of a tootheddrive, these grooves and webs engage with one another in certain regionsof the spherical surface, so that the desired drive takes place. It isof no significance which drive element is rotated by the driving shaftand which drive element drives the outgoing shaft.

Such a force transfer, in which both drive elements are cylindrical, isknown in connection with screw tools from German Pat. No. 17 28 574 andis commercially available under the trademark TORX. The cylindricalconstruction of both drive elements ensures that sloping or inclining ofthe tool is not possible, the axis of the screw and the associated tool(wrench) being aligned with one another.

According to the invention an articulated joint is obtained in which theaxes of the two shafts can be pivoted with respect to one another by acertain amount. On pivoting or tilting the axes of the two shaftsintersect roughly in the centre of the spherically constructed part ofthe second drive element. If this spherical part is compared with theglobe, the drive element axis coinciding with the earth's axis, thegroove-like depressions or web-like elevations run roughly in accordancewith degrees of longitude on the globe, whilst the inner face of thefirst drive element engages roughly corresponding to a circumferentialline of the globe, which intersects the equator.

Preferably, the drive elements have in each case six depressions betweensix elevations.

According to a construction of the invention the transitions between thedepressions and elevations are gradual, so that everything is roundedand sharp edges are avoided. Preferably the median plane (plane ofsymmetry) of each depression or elevation contains the rotation axis ofthe particular drive element. This means that the shafts can easily bepivoted with respect to one another and the transferred force hasvirtually no action on the pivoting.

According to a preferred embodiment on the spherical, second driveelement the depressions are at least in part narrower than theelevations of the first drive element or the elevations are at least inpart narrower than the depressions of the first drive element. As aresult the necessary clearance exists, so that jamming is avoided duringpivoting or tilting. Due to the depressions and elevations becomingnarrower, as from the equatorial zone of the spherical drive element andtowards the two poles, the shafts are pivotably engageable with oneanother.

The three-dimensional pivot angle of the spherical articulated joint inthe case of the spherical drive element on the one hand results from thenarrowing flank, included or bevel angles of the maxima of the convexelevation or the minima of the concave depression and the turning orreversal points thereof from the equatorial plane to the pole or polarcaps and on the other hand in the case of the hollow drive elementthrough the constant flank, included or bevel angles obtained from themaxima of the convex elevation and the minima of the concave depressionand their turning or reversing points. The geometry of the hollow driveelement is congruent with the spherical geometry in its equatorialplane.

The perimeter in the maximum of the convex elevation and the innercircle in the minimum of the concave depression are defined by A and Bin TORX drive elements. The convex radius is designated F_(Rad) and theconcave radius E_(Rad). In the case of TORX F_(Rad) <E_(Rad). Thecentres of these radii are located on different circles. The convex andconcave radii passing into one another form reversing points formingangles to the maximum of the convex elevation and the minimum of theconcave depression and which are referred to as convex and concave flankangles. Passing from the equatorial plane of the spherical drive elementto the two poles the elevations and depressions become narrower or theconvex and concave flank angles become smaller. In the transition to thepoles, the convex and concave flank angles no longer form a commontangent and instead constitute two crossing tangent jump functions. Theangles of the maximum and minimum to the reversing points pass into avertical line in the poles.

For manufacturing reasons the spherical drive element is not extended tothe north pole or south pole. There are no north and south sphericalportions, so that there is a spherical layer as the drive.

The three-dimensional swivel angle is obtained on the one hand from thedifference of the dihedral angles γ1+γ2 (in radian measure) of thespherical wedges of pole N to reversal points A and B of the convex andconcave radii or from the tapering flank angles of the convex andconcave flanks from the equator to the poles of the spherical drive andon the other hand from the constant flank angles of the hollow driveelement and the clearance resulting from the geometrys of the two driveelements.

The convex and concave radii of the hollow drive element arecomplimentary to the geometry in the equatorial plane of the sphericaldrive element.

In order to increase this clearance, or if the driving and driven shaftis connected to a frame or casing, which largely surrounds the sphereand must naturally give a pivot angle, the centre of the inner circlewhich is tangent to the minimum of the concave depression is set by aminimum amount below the sphere centre.

The semi-circle or hemisphere in the north pole, with the same radius ofthe inner circle, thus has a larger difference between the perimeter orsphere external diameter in the north pole and the smaller sphere in thenorth pole resulting from the new inner circle in the minimum of theconcave depression with the displaced centre. Thus, the reversal pointsof the convex and concave radii change their position in the interior ofthe sphere. Thus, the angles of the maximum of the convex elevation orthe minimum of the concave depression becomes smaller towards thereversal points.

The centre of the inner circle for the south pole is set above thesphere centre by the same given amount. The semicircle or hemisphere inthe south pole, with the same radius of the inner circle, acquires thesame large difference between the perimeter or sphere external diameterin the south pole and the smaller sphere in the south pole, as shown bythe sphere geometry on the northern hemisphere. The clearance betweenthis created drive sphere and the hollow cylinder with the complimentarygeometry in the equatorial plane of the spherical drive element orframe, which largely surrounds the sphere and has an inner circle in theminimum of the concave depression with the same centre, gives thethree-dimensional angle of the drive element obtained during pivoting.

The functions are calculated from the mechanical relationships of thespherical triangle and the oblique-angled triangle.

According to a special embodiment on the spherical drive element thedepressions and elevations in the equatorial zone correspond as regardswidth to the associated elevations and depressions of the first driveelement and with increasing distance from the equatorial zone thedepressions become wider and the elevations narrower. If the inside ofthe first drive element contacts the sphere surface in the vicinity ofthe equatorial zone, the pitch of the depressions and elevations on thesphere precisely correspond to those on the inner wall of thecylindrical first drive element, so that there is no risk of jamming.With increasing pivoting the cylindrical inner phase, at least partlyengages with part of the sphere, where the grooves or webs are closertogether in accordance with the degrees of longitude on the globe, sothat it can be appropriate in these areas to allow a certain clearance,which leads to a reduction in the convex and concave flank angles.

These and other features of the invention are pointed out in the claims.Other objects and advantages of the invention will become evident fromthe following detailed description when read in light of theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 an open or detachable articulated joint.

FIGS. 2 and 3 parts of the articulated joint, which can be fixed to oneanother.

FIG. 4 a plan view of the parts in FIG. 3.

FIG. 5 an articulated joint according to FIG. 3 in which two positionsof the second shaft with the second drive element fitted thereto areshown.

FIG. 6 an illustration of the invention on a sphere geometry.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 a head piece is fitted to a first shaft and is formed by aroughly hollow cylindrical part 2, which is shown in sectional form inFIG. 1. Hollow cylinder 2 forms the first drive element or thecylindrical hollow drive element.

A view of a shaft 3 is provided in the lower part of FIG. 1 and itsupper end is connected via a neck 4 to a spherical second drive element5, i.e. the spherical drive element. Both drive elements 2 and 5correspond in the equatorial plane to TORX geometry (FIG. 6).

FIG. 4 shows the cylindrical hollow drive element 2 in plan view alongline A--A. On its inside, it has six somewhat widened elevations 6uniformly distributed about its longitudinal axis and between them arearranged in regularly distributed manner six narrower depressions 7.Compared with a circular circumferential line, a wavy profile is formed,which extends in axially parallel manner from the outer edge 2a ofhollow drive element 2 towards the inside. Facing parts of depressions 7have a spacing a and facing points of the elevations 6 a correspondinglysmaller spacing b.

The spherical drive element 5 on the second shaft 3 carries widerdepressions 8, between which there are narrower elevations 9.

In the section A--A according to FIG. 4, it can be seen that the equatorof the spherical drive element 5 and the hollow drive element 2 are incontact in the plane indicated B--B in FIG. 1, because in the equatorialregion of spherical drive element 5, its depressions 8 and elevations 9have a roughly complimentary configuration to the elevations 6 anddepressions 7 on the inner face of the hollow drive element 2. As shownby FIG. 1, the upper polar cap of the spherical drive element 5 is cutoff at right angles to the axis of shaft 3, so that FIG. 4 shows acircular line 10 towards which run the depressions and elevations of thespherical surface.

In the embodiment according to FIG. 1, shaft 1 with the hollow driveelement 2 can be freely mounted on the spherical drive element 5 of theshaft. Thus, if in the represented position the two shafts are securedagainst axial displacement, the represented articulated joint can beused without further parts.

Thus, an articulated joint according to FIG. 1 can be used as a screwand wrench. Thus, in accordance with the dotted line 11, on hollow driveelement 2 a screw head 11a can be connected to a screw shank 11b. To acertain extent shaft 3 then belongs to a wrench, which can turn screw11a, 11b with the spherically constructed drive element 5. As a resultof the spherical construction, it is easy to insert such a wrench intothe cylindrical part of the hollow drive element 2 and during screwingthere is no need for the wrench axis to be aligned with the screw axis.It is therefore easier to actuate more difficultly accessible screwheads, even if the field of vision is restricted during actuation.

On spherical drive element 5, the depressions 8 compared with theelevations 6 of the hollow drive element 2 are appropriately narrowerwith increasing distance from the equatorial zone of the spherical part,i.e. towards the poles or the roughly web-shaped elevations 9 becomenarrower compared with the roughly groove-shaped depression 7 on theinner face of the first drive element 2. Thus, even in the case ofsomewhat greater pivoting of shafts 1 and 3 with respect to one another,there is no jamming between the two drive elements.

The three-dimensional swivel angle of the spherical articulated joint inthe case of the spherical drive element is obtained on the one hand fromthe narrowing flank angles of the maxima of the convex elevation or theminima of the concave depression and their turning points from theequatorial plane to the polar caps and on the other hand in the case ofthe hollow drive element through the constant flank angles resultingfrom the maxima of the convex elevation and the minima of the concavedepression and their turning points. The geometry of the hollow driveelement is congruent with the sphere geometry in its equatorial plane.

FIG. 3 shows an embodiment, in which the spherical drive element 5 isconstructed in the same way as in FIG. 1. However, instead of beingprovided with a round shaft, it is connected to a shaft or shank portion12, which e.g. has a square or hexagonal surface and can be connected toa drive in some way, e.g. by clamping.

The hollow drive element is constructed as an upwardly open hollowcylinder 13, which has the same wavy profiling on its inside asdescribed relative to FIGS. 1 and 4.

Section A--A of FIG. 1 shown in FIG. 4 corresponds in view and outlineswith the plan view of FIG. 3, the plan view on drive element 13 takingthe place of the section through hollow drive element 2.

According to FIG. 3, the cylindrical hollow drive element 13 isinternally beaded on its lower end and consequently engages behind thespherical drive element 5 in such a way that the latter cannot be drawnout of drive element 13.

FIG. 2 illustrates a device for driving the element 13. The top ofelement 13 can receive, and have fixed therein, a coupling 14 having anapproximately cylindrical surface complimentary to the surface of theinner face of the drive element 13. The coupling 14 axially extends froma shaft 15.

In front of the lower face 16 of part 14 and surface 17 of sphericaldrive element 5 adequate space must be provided to allow a pivoting ofthe sphere. Parts 13 and 14 co-operate in the same way as the known headand wrench construction according to German Pat. No. 17 28 574.

In an articulated joint according to FIGS. 2 and 3 the driving shaft 12or 15 and the driven shaft 15 or 12 cannot move away from one anotherand the first drive element 13 acts as a frame or casing substantiallysurrounding sphere 5, which prevents the penetration of dirt.

FIG. 5 shows on a larger scale drive element 13 according to FIG. 3,which embraces the spherical drive element 5, which can be pivoted indotted line manner in two directions out of the aligned position and inopposite directions by an angle γ. This pivoting shown in the drawingplane of FIG. 5 can naturally take place in all directions, i.e. alsoupwards and downwards.

Lines 18 and 19 illustrate the central planes of sphere 5, which can bepivoted upwards or downwards by angle γ with respect to the position ofline 20, which corresponds to the position with axes aligned.

Thus, the articulated joint according to the invention has five degreesof freedom, namely two for the rotation directions and three for thethree-dimensional angle γ.

Thus, a reliable coupling is obtained between the two shafts,independently of which shaft serves as the drive and which shaft isdriven. As a result of the positive connection between the profiledsurfaces the specific loading of the materials is reduced, so that it ispossible to prevent deformation, particularly due to shear forces, suchas can occur with normal hexagon spanner arrangements.

As a result of the inventive construction three-dimensional pivotabilityexists between the hollow drive element 2 and the spherical driveelement 5, the latter comprising sphere circles corresponding to the Aand B points of a TORX, A and B being located in the same centre plane(FIG. 6). The three-dimensional pivot angle is obtained from thedecreasing convex (K1) and concave (K2) angles on the spherical driveelement 5 compared with the constant convex and concave angles on thehollow drive element 2.

I claim:
 1. An articulated joint comprising a first drive element at theend of a first rotary shaft and a second drive element at the end of asecond rotary shaft, said drive elements being pivotably engageable insuch a way that the axes of the shafts can be pivoted with respect toone another up to a given angle, characterized in that the first driveelement is shaped substantially like a hollow cylinder and is providedon its inner face with axis-parallel, uniformly circumferentiallydistributed, alternately convex and concave depressions and elevationswhich pass into one another and that the second drive element issubstantially spherical and has on its surface alternating depressionsand elevations which run in the longitudinal direction in planescontaining the axis of the second shaft and having in thecircumferential direction, along the equatorial plane of the sphericalsecond drive element, a configuration complimentary to the inner face ofthe first drive element, said spherical second element forming aspherical body greater than half a sphere, the concave and convexdepressions and elevations on said cylindrical first drive element beingstraight along the axis of the first element and extending a distancealong the axis of the first element longer than the spherical secondelement; said spherical second element having a spherical center andfirst and second hemispheres on each side of the center along the axisof the second element, the depressions in said second element havingminima extending along respective circular arcs each in a plane of theaxis of the shaft of said second element, the circular arcs in eachhemisphere having a center axially offset from the spherical center inthe direction of the other hemisphere.
 2. An articulated joint accordingto claim 1, characterized in that on the spherical second drive elementthe depressions are at least partly narrower than the elevations of thefirst drive element.
 3. An articulated joint according to claim 2,characterized in that on the spherical drive element, the depressionsand elevations in an equatorial plane have a width corresponding to theassociated elevations or depressions of the first drive element and thedepressions and elevations become narrower as the distance from theequatorial zone increases.
 4. An articulated joint according to claim 1,characterized in that on the spherical second drive element theelevations are at least partly narrower than the depressions on thefirst drive element.
 5. An articulated joint comprising a first driveelement at the end of a first rotary shaft and a second drive element atthe end of a second rotary shaft, said drive elements being pivotablyengageable in such a way that the axes of the shafts can be pivoted withrespect to one another up to a given angle, characterized in that thefirst drive element is shaped substantially like a hollow cylinder andis provided on its inner face with axis-parallel, uniformlycircumferentially distributed, alternately convex and concavedepressions and elevations which pass into one another and that thesecond drive element is substantially spherical and has on its surfacealternating depressions and elevations, which run in the longitudinaldirection in accordance with a plane containing the axis of the secondshaft and having in the circumferential direction, particularly in theequatorial plane of the spherial second drive element a configurationroughly complimentary to the inner face of the first drive element,saidelevations on said spherical second element being circumferentiallyconvex and the depressions on said second element beingcircumferentially concave and merging circumferentially into saidelevations on said spherical second element, said depressions on thespherical second element being circumferentially larger than saidelevations, on said first element said elevations beingcircumferentially convex and said depressions being circumferentiallyconcave and circumferentially merging into each other smoothly, withsaid elevations being circumferentially larger than said depressions;said spherical second element having a spherical center and first andsecond hemispheres on each side of the center along the axis of thesecond element, the depressions in said second element having minimaextending along respective circular arcs each in a plane of the axis ofthe shaft of said second element, the circular arcs in each hemispherehaving a center axially offset from the spherical center in thedirection of the other hemisphere.
 6. An articulated joint according toclaim 5, characterized in that each of the drive elements has sixdepressions between six elevations.
 7. An articulated joint according toclaim 6, characterized in that the circumferential transitions betweendepressions and elevations in the first drive element are continuous. 8.An articulated joint according to claim 6, characterized in that on thespherical drive element the depressions and elevations in equatorialplane have a width corresponding to the associated elevations ordepressions of the first drive element and the depressions becomenarrower as the distance from the equatorial zone increases.
 9. Anarticulated joint according to claim 5, characterized in that thetransitions between depressions and elevations on said first element arecontinuous.
 10. An articulated joint according to claim 9, characterizedin that the median plane of each depression or elevations contains therotation axis of the particular drive element.
 11. An articulated jointaccording to claim 9, characterized in that on the spherical driveelement the depressions and elevations in equatorial plane have a widthcorresponding to the associated elevations or depressions of the firstdrive element and the depressions become narrower as the distance fromthe equatorial zone increases.
 12. An articulated joint according toclaim 5, characterized in that the median plane of each depression orelevation contains the rotation axis of the particular drive element.13. An articulated joint according to claim 12, characterized in that onthe spherical drive element the depressions and elevations in equatorialplane have a width corresponding to the associated elevations ordepressions of the first drive element and the depressions becomenarrower as the distance from the equatorial zone increases.
 14. Anarticulated joint according to claim 5, characterized in that on thespherical drive element the depressions and elevations in equatorialplane have a width corresponding to the associated elevations ordepressions of the first drive element and the depressions becomenarrower as the distance from the equatorial zone increases.
 15. Anarticulated joint comprising a first drive element at the end of a firstrotary shaft and a second drive element at the end of a second rotaryshaft, said drive elements being pivotably engageable in such a way thatthe axes of the shafts can be pivoted with respect to one another up toa given angle, characterized in that the first drive element is shapedsubstantially like a hollow cylinder and is provided on its inner facewith axis-parallel, uniformly circumferentially distributed, alternatelyconvex and concave depressions and elevations which pass into oneanother and that the second drive element is substantially spherical andhas on its surface alternating depressions and elevations, which run inthe longitudinal direction in accordance with a plane containing theaxis of the second shaft and having in the circumferential direction,particularly in the equatorial plane of the spherical second driveelement a configuration roughly complimentary to the inner face of thefirst drive element,said spherical second element having a sphericalcenter and first and second hemispheres on each side of the center alongthe axis of the second element, the depressions in said second elementhaving minima extending along respective circular arcs each in a planeof the axis of the shaft of said second element, the circular arcs ineach hemisphere having a center axially offset from the spherical centerin the direction of the other hemisphere.
 16. An articulated joint as inclaim 15, characterized in that each of the drive elements has sixdepressions between six elevations.
 17. An articulated joint accordingto claim 16, characterized in that the median plane of each depressionor elevation contains the rotation axis of the particular drive element.18. An articulated joint according to claim 16, characterized in that onthe spherical second drive element the depressions are at least partlynarrower than the elevations of the first drive element.
 19. Anarticulated joint according to claim 16, characterized in that thetransitions between depressions and elevations on said first element arecontinuous.
 20. An articulated joint according to claim 19,characterized in that the median plane of each depression or elevationcontains the rotation axis of the particular drive element.
 21. Anarticulated joint according to claim 19, characterized in that on thespherical second drive element the depressions are at least partlynarrower than the elevations of the first drive element.
 22. Anarticulated joint according to claim 19, characterized in that on thespherical second drive element the elevations are at least partlynarrower than the depressions on the first drive element.
 23. Anarticulated joint according to claim 16, characterized in that on thespherical second drive element the elevations are at least partlynarrower than the depressions on the first drive element.
 24. Anarticulated joint according to claim 15, characterized in that themedian plane of each depression or elevation contains the rotation axisof the particular drive element.
 25. An articulated joint according toclaim 15, characterized in that on the spherical second drive elementthe depressions are at least partly narrower than the elevations of thefirst drive element.
 26. An articulated joint according to claim 15,characterized in that on the spherical second drive element theelevations are at least partly narrower than the depressions on thefirst drive element.